Detection of thermospheric vertical wind oscillations at El Leoncito Observatory in Argentina (31.8 S, 69.3W)

Examination of Fabry-Perot interferometer (FPI) observations of vertical and horizontal winds and temperatures obtained on the nights of 18-19, 19-20, and 20-21 October, 2023, and selected nights on May 2024, December 2024, and March 2025 from El Leoncito Observatory (31.8 S, 69.3 W) show the appearance of vertical wind oscillations (VWO) with amplitudes of 10 to 30 ms−1 and periods of 30 to 40 minutes. Similar perturbations are also seen in the FPI relative intensity and temperature data as well as in the 630 nm brightnesses observed by a co-located all-sky imager. Lomb-Scargle periodogram analysis of the VWO and dTEC data confirms that a dominant periodicity is seen at 0.6±0.1 hr for the VWO data but not for the dTEC data. Analysis of GNSS data obtained on 19-20 October, 2023, for the region between 30 S to 40 S for the period between 0254 and 0358 UT by the South American network of GNSS receivers show the existence of a wave train in the horizontal plasma distribution propagating in a nearly southwest direction within the range of 20 to 40 degrees west of south with a speed of ∼165±25 ms−1, a horizontal wavelength of ∼450±25 km and a typical TEC amplitude of 0.2 TEC. Examination of the ionospheric electron density peak altitude (hmF2) data obtained by ionosondes located at Tucuman (26.9 S, 65.4 W), Bahia Blanca (38.7 S, 62.3 W), and Chillan (36.6 W, 72.10 W) as well as Lomb-Scargle periodograms revealed the existence of fluctuations for the Bahia Blanca site but not for either of the other two sites. The VWO amplitudes are found to be significantly weaker for two nights in the local summer, i.e., ∼ 10-15 ms−1, as compared with the equinox and winter results, i.e., ∼20 to 30 ms−1. We suggest that these observed fluctuations in optical, GPS, and ionosonde data are produced as a result of westerly surface winds passing over the Andes Mountains, a phenomenon similar to the production of thermospheric wave structure as described in the modeling work of Lund et al. (2020) and Fritts et al. (2021) for the case of westerly surface winds crossing the Andes mountains in South America.